The present invention relates generally to an ion exchange membrane electrolyzer, and more particularly to a bipolar filter press type ion exchange membrane electrolyzer.
A currently available bipolar filter press type ion exchange membrane electrolyzer built up of a number of electrolyzer cell units stacked one upon another via ion exchange membranes, wherein each electrolyzer cell unit comprises an anode partition and a cathode partition which are mechanically and electrically joined together.
FIGS. 8(A) and 8(B) are illustrative of one conventional ion exchange membrane electrolyzer.
FIG. 8(A) is a schematic of one electrolyzer cell unit for a bipolar ion exchange membrane electrolyzer as viewed from an anode chamber, and FIG. 8(B) is a sectional view taken on line A—A of FIG. 8(A).
An anode chamber partition 54 and a cathode chamber partition 55 forming an anode chamber 52 and a cathode chamber 53 of an electrolyzer cell unit 51 are provided with anode ribs 56 and cathode ribs 57 at given intervals. Each anode rib 56 is provided with an anode 58, while each cathode rib 47 is provided with a cathode 59.
For an ion exchange membrane electrolyzer having a height of 1 m or so in its longitudinal direction and a width of 2 m or so in the lateral direction, it is required to decrease the concentration distribution of electrolyte in each electrode chamber, thereby carrying out electrolysis with efficiency. Decreasing the concentration distribution within the electrode chamber may be achieved by a method of circulating electrolyte with an externally provided electrolyte-circulating pump. There is also available another method that dispenses with any external circulating pump, in which the electrolyte is circulated by use of the buoyancy force of the gas generated by electrolysis. So far, it has been proposed to locate an internal circulation member in the electrode chamber for the purpose of achieving smooth internal circulation.
However, the location of the internal circulation member in the electrode chamber in addition to anode and cathode ribs leads to the need of many other members for the construction of an electrolyzer, and the performance of internal circulation is still less than satisfactory.
FIGS. 9(A) and 9(B) are illustrative of a prior art ion exchange membrane electrolyzer of another construction.
FIG. 9(A) is a schematic of an electrolyzer cell unit for a bipolar type ion exchange membrane electrolyzer as viewed from an anode chamber side, and FIG. 9(B) is a perspective view of a partition.
The electrolyzer shown in FIGS. 9(A) and 9(B) is a bipolar type ion exchange membrane electrolyzer proposed by the present applicant in U.S. Pat. No. 5,314,591, etc.
In an electrolyzer cell unit 51, an anode chamber partition 54 and a cathode chamber partition forming an anode chamber 52 and a cathode chamber, respectively, are provided with recess/projection combinations of similar configuration, which engage the anode chamber partition 54 integrally with the cathode chamber partition, so that a mixed gas-liquid fluid generated at the electrode goes up along a recess 60 and electrolyte goes down between an electrolyte-circulating path-forming member 61 located in the electrode chamber and the anode chamber partition 54, thereby ensuring the internal circulation of electrolyte in the electrolyzer. In this electrolyzer, the circulation of electrolyte leaves a good deal to be desired because the electrolyte-circulating path is defined by a space between the electrolyte-circulating path-forming member and the partition having a recess/projection combination.
A primary object of the present invention is to provide an ion exchange membrane electrolyzer which has great rigidity with improvements in the internal circulation of electrolyte that makes use of an upward flow of the gas generated in the anode and cathode chambers and a downward flow of electrolyte from which the gas is removed and, hence, an improved electrolysis efficiency.